Weather related mortality in high-, middle- and low-income countries - differences and similarities

Abstract

Background. The increased number of publication of time series studies of the short term effects of weather on daily mortality facilitates a more detailed comparison of temperature- (and rainfall) mortality functions across populations. There is a lack of evidence regarding weather effects in tropical and sub-tropical climates. Aims. To review published studies on weather effects on daily mortality in low, middle and high income countries, and describe important differences in response functions between populations. Methods. Review published studies that quantify the impact of temperature and rainfall on daily mortality outcomes in populations in high, middle and low income countries. Results: Published studies from low income countries or in tropical climates include several from the CLIMIMO collaboration that used demographic surveillance data from the inDEPTH network. Both high and low temperatures increase the risk of acute mortality in most populations in low and middle-income countries, with cold effects dominating in some populations. The heat and cold effect estimates (slopes) and thresholds are quite heterogeneous. Differences in effects in adults, children and the elderly reflect the underlying disease profiles, particularly where mortality from infectious diseases is high. Rainfall effects are particularly important in rural populations where malaria mortality is high. Conclusions: Population specific weather-health relationships are determined by climate and non-climate factors. Urban and rural populations in low and middle income settings have different health profiles and socio-economic determinants of health status which make them more susceptible to weather effects, particularly in children. Epidemiological analyses can provide limited information on the causal mechanisms by which environmental temperature and rainfall affect acute mortality. Lack of long-term and daily time series data on health outcomes in low income settings remains a limitation to research on short-term health effects.